Method and apparatus for recording magnetic resonance data

Abstract

In a method and apparatus for recording magnetic resonance (MR) data of a target region of a subject, the recording process is divided into subsections each follow the other after a repetition time. Before each recording of MR data of a subsection with a measurement sequence, an adiabatic preparatory pulse is activated that inverts the longitudinal magnetization of a saturation molecule type, from which no MR data are to be recorded. An excitation pulse is emitted spaced by an inversion time from the preparatory pulse. Before the first preparatory pulse, at least one adiabatic preparation pulse is emitted that inverts the longitudinal magnetization with a timing such that the longitudinal magnetization of the saturation molecule type at the time of the first preparatory pulse at a steady state value, which occurs again before the repetition time after each preparatory pulse.

The invention claimed is: 
     
       1. A method for recording magnetic resonance (MR) data, comprising:
 in a computer, dividing a procedure for acquiring MR data from a target region of a subject into a plurality of successive procedure subsections, each having a same repetition time that starts at a beginning of each procedure subsection and ends at a beginning of a next-successive procedure subsection, each procedure subsection comprising a measurement sequence in which the MR data are acquired in that procedure subsection, each measurement sequence beginning with radiation of an excitation pulse; 
 from said computer, operating an MR data acquisition scanner in order to acquire said MR data by executing said procedure and, before the excitation pulse of each measurement sequence, activating an adiabatic preparatory pulse that inverts a longitudinal magnetization of a saturation molecule type in the subject from which no MR data are to be acquired, said excitation pulse following said adiabatic preparatory pulse by an inversion time; 
 from said computer, also operating said MR data acquisition scanner in said procedure by, before a first activation of said adiabatic preparatory pulse, activating at least one adiabatic preparation pulse that inverts said longitudinal magnetization, with a timing between said at least one adiabatic preparation pulse and said first adiabatic preparatory pulse causing said longitudinal magnetization to be at a steady state value at a time of activation of said first preparatory pulse, said steady state value again occurring after activation of each adiabatic preparatory pulse and before an end of each repetition time; and 
 in said computer, compiling said MR data in a data file and making said data file available from said computer as an electronic output. 
 
     
     
       2. A method as claimed in  claim 1  comprising, in said computer, determining said determining said timing between said at least one adiabatic preparation pulse and said adiabatic preparatory pulse by accessing a time interval from a look-up table or calculating a time interval from a functional mathematical relationship depending on a basic magnetic field strength in said scanner, a relaxation time of said saturation molecule, and said repetition time. 
     
     
       3. A method as claimed in  claim 1  comprising activating a single adiabatic preparation pulse before said adiabatic preparatory pulse with a time interval therebetween that causes the steady state value of said longitudinal magnetization to occur at the time of activation of said adiabatic preparatory pulse. 
     
     
       4. A method as claimed in  claim 1  comprising activating two adiabatic preparation pulses that are spaced from each other by a time interval, with said first adiabatic preparatory pulse following a second of said adiabatic preparation pulses by a further time interval, with said further time interval being selected so that, by relaxation of said longitudinal magnetization, a negative of an intermediate value of said longitudinal magnetization is produced, with said steady state value being reached by said relaxation during said further time interval, starting from said intermediate value, after activation of said second of said adiabatic preparation pulses. 
     
     
       5. A method as claimed in  claim 1  comprising:
 in said computer, identifying whether a predetermined region in the subject exists in which said MR data acquisition scanner can be operated in either of a first mode or a second mode; 
 said first mode comprising activating a single adiabatic preparation pulse before said adiabatic preparatory pulse with a time interval therebetween that causes the steady state value of said longitudinal magnetization to occur at the time of activation of said adiabatic preparatory pulse; 
 said second mode comprising activating two adiabatic preparation pulses that are spaced from each other by a time interval, with said first adiabatic preparatory pulse following a second of said adiabatic preparation pulses by a further time interval, with said further time interval being selected so that, by relaxation of said longitudinal magnetization, a negative of an intermediate value of said longitudinal magnetization is produced, with said steady state value being reached by said relaxation during said further time interval, starting from said intermediate value, after activation of said second of said adiabatic preparation pulses; 
 in said computer, selecting whether to operate said MR data acquisition scanner in said first mode or in said second mode in order to minimize an overall duration of said procedure. 
 
     
     
       6. A method as claimed in  claim 5  comprising, outside of said predetermined area, operating said MR data acquisition scanner in order to execute said procedure using a non-adiabatic, spectrally selective preparation pulse instead of said at least one adiabatic preparation pulse. 
     
     
       7. A method as claimed in  claim 1  comprising, from said computer, operating said MR data acquisition scanner in said procedure to activate a spoiler gradient pulse, after each adiabatic preparation pulse, that clears any remaining transverse magnetization in said subject. 
     
     
       8. A method as claimed in  claim 1  comprising, from said computer, operating said MR data acquisition scanner in said procedure to activate each preparatory pulse and said at least one preparation pulse as SPAIR pulses. 
     
     
       9. A method as claimed in  claim 1  wherein said saturation molecule type is fat molecules. 
     
     
       10. A magnetic resonance (MR) apparatus comprising:
 an MR data acquisition scanner; 
 a computer configured to divide a procedure for acquiring MR data from a target region of a subject into a plurality of successive procedure subsections, each having a same repetition time that starts at a beginning of each procedure subsection and ends at a beginning of a next-successive procedure subsection, each procedure subsection comprising a measurement sequence in which the MR data are acquired in that procedure subsection, each measurement sequence beginning with radiation of an excitation pulse; 
 said computer being configured to operate said MR data acquisition scanner in order to acquire said MR data by executing said procedure and, before the excitation pulse of each measurement sequence, to activate an adiabatic preparatory pulse that inverts a longitudinal magnetization of a saturation molecule type in the subject from which no MR data are to be acquired, said excitation pulse following said adiabatic preparatory pulse by an inversion time; 
 said computer being configured to also operate said MR data acquisition scanner in said procedure by, before a first activation of said adiabatic preparatory pulse, activating at least one adiabatic preparation pulse that inverts said longitudinal magnetization, with a timing between said at least one adiabatic preparation pulse and said first adiabatic preparatory pulse causing said longitudinal magnetization to be at a steady state value at a time of activation of said first preparatory pulse, said steady state value again occurring after activation of each adiabatic preparatory pulse and before an end of each repetition time; and 
 said computer being configured to compile said MR data in a data file and make said data file available from said computer as an electronic output. 
 
     
     
       11. A non-transitory, computer-readable data storage medium encoded with programming instructions, said storage medium being loaded into a computer system of a magnetic resonance (MR) apparatus that comprises an MR data acquisition scanner, said programming instructions causing said computer system to:
 divide a procedure for acquiring MR data from a target region of a subject into a plurality of successive procedure subsections, each having a same repetition time that starts at a beginning of each procedure subsection and ends at a beginning of a next-successive procedure subsection, each procedure subsection comprising a measurement sequence in which the MR data are acquired in that procedure subsection, each measurement sequence beginning with radiation of an excitation pulse; 
 operate said MR data acquisition scanner in order to acquire said MR data by executing said procedure and, before the excitation pulse of each measurement sequence, activating an adiabatic preparatory pulse that inverts a longitudinal magnetization of a saturation molecule type in the subject from which no MR data are to be acquired, said excitation pulse following said adiabatic preparatory pulse by an inversion time; 
 also operate said MR data acquisition scanner in said procedure by, before a first activation of said adiabatic preparatory pulse, activating at least one adiabatic preparation pulse that inverts said longitudinal magnetization, with a timing between said at least one adiabatic preparation pulse and said first adiabatic preparatory pulse causing said longitudinal magnetization to be at a steady state value at a time of activation of said first preparatory pulse, said steady state value again occurring after activation of each adiabatic preparatory pulse and before an end of each repetition time; and 
 compile said MR data in a data file and make said data file available from said computer system as an electronic output.